Destination Mars

by Rod Pyle

  Soon another result came in, supplying a broadly opposite picture of another part of Mars. When the region called Ganges Chasm was investigated, a huge deposit of the mineral olivine was discovered. Olivine is soluble in water over time, so this large an area of the mineral indicated a long dry period in the region. The infrared imaging was also allowing planetary scientists to develop a far better idea of mineralogical distribution, lava flows, and soil types. All this was derived from observing thermal or temperature differences between one area and another, as seen in daytime and then at night when the more slowly cooling areas (indicative of differing soil and rock types) were clearly visible in this invisible spectrum. Not only do different kinds of rocks cool at different rates, but sand and sedimentation (dirt, pebbles, boulders) of a given type of rock cool faster than a solid mass of the same material. So the temperature measurements showed broad swaths of geological and erosional formations, allowing the paint-by-numbers map of Mars to be filled in, for the first time, with some authority.

  These results did much to redeem JPL in the public eye, as well lift the spirits of those who labored there and at affiliated institutions. But there was more to come. The gamma-ray spectrometer was showing the planetwide distribution of ice under the surface, demonstrating far more water than even optimistic projections had predicted. This helped to answer the question of where all the water had come from to form the many huge, water-created features seen across the surface, and ruled out some of the more farfetched hypotheses. Mars was now confirmed as having a currently living (if less so than Earth's) environment, and the Red Planet was far from the dead place it had appeared to be so long ago in the fuzzy Mariner 4 pictures. There was clearly water—if not gold—in those hills out yonder.

  Look at it this way: not all the visual images coming back were of much higher quality, and in some cases less so, than the previous Mars Global Surveyor. But the thermal information was almost three hundred times better. So until now, scientists had been forced to deduce geological and environmental conditions from images that could see nothing smaller than a schoolbus—not as useful as they desired. But the new and highly detailed thermal information from Mars Odyssey showed what was below the sand, what existed in large areas invisible to the naked eye, painting a larger and better-defined map of the surface composition.

  But wait, as the Ginsu® salesman said, there is more.

  The instruments also showed large areas of bare rock where the excessive dust and sand found all over Mars had been scoured away, as well as large deposits of rubble at the base of hillsides and mountains. This was a dead giveaway that weather was hard at work on Mars, reinforcing the notion that, while dry and dusty, there was a vibrant meteorological system at work on Mars.

  As the days grew colder in the Martian winter of the northern hemisphere, the expected dry ice layer appeared. But when it retreated, a dense layer of permafrost—water ice in the soil—was quickly apparent below. Again, water, water, everywhere, even if it was frozen. This was good news for those seeking possible habitats for some form of life on Mars.

  This was remote science at its best. In many cases, incomplete answers from Mars Odyssey were fleshed out by data from Mars Global Surveyor and vice versa. The two spacecraft were working in tandem—each according to its strengths—to develop a clearer, planetwide picture of Mars. And this gave scientists something else they had been lacking heretofore: context.

  The picture of Mars that was emerging was an intriguing one. Water ice was found widely distributed across the planet. The concentrations lean out nearer the equator; in the polar regions, one might find a half pound of water per pound of soil, or 50 percent water by weight. Closer to the equator, this falls to 2–10 percent. There were exceptions though. Arabia Terra, an almost 2,000-mile-wide equatorial desert, and other equatorial exceptions showed indications of large masses of water. Mars was much more complicated than most had thought.

  It is worth noting that the water masses are, in some areas, projected to be about half a mile deep. But the instrumentation on these orbiters was able to measure only about a yard down, so anything beyond that is theoretical. However, this deep water-mass projection does come close to resolving the mystery of the missing water on Mars as regards total mass.

  One more shock awaited. The MARIE experiment, designed to measure radiation in the Martian orbital environment, presented a surprising picture: the amount of radiation, the kind that might put future astronauts at risk, was at least double that of Earth. As a control, measurements were taken aboard the International Space Station during roughly the same period. The experiment had previously been used on both the station and the shuttle, but this was the first time it had left Earth orbit. MARIE measured both solar radiation and galactic cosmic rays. The result? Astronauts spending extended periods in the Martian orbital environment would need extra protection from radiation. The experiment ended when a spike in solar flares appeared to have overloaded the device.

  But Mars Odyssey had one more trick up its sleeve. By the time it had reached its first Martian year of operation—687 Earth days—it had been pressed, as planned, into being a relay station for the newly landed Mars Exploration Rovers. A full 75 percent of the early images from the rover Spirit were relayed through Odyssey, and the orbiter continued to render assistance for the life of Spirit (until it ceased function), as it continues to for the rover Opportunity.

  And Mars Odyssey has earned one more distinction. In late 2010, it broke Mars Global Surveyor's record as the longest operational spacecraft at Mars: 3,340 days. It is still going strong and continues to provide data, imaging, and relay capability for other missions.

  While it may not look much like the Energizer Bunny®, Mars Odyssey just keeps going, and going, and going…

  Jeffrey Plaut started his college education studying music composition but was unable to maintain his allegiance to Bach and Beethoven. He can often be found on the porch of his small home at the foothills a few miles east of JPL in Sierra Madre, a small hamlet that resembles Mayberry as much as a Southern Californian suburb. From his back patio, with a view of the nearby San Gabriel Mountains, he is as likely to be listening to Jimi Hendrix as Joseph Hayden. He is not able to spend as much time as he would like with his wife and two young daughters due to his long and rewarding involvement with Mars Odyssey. From his home he recalls those formative college years:

  “There were several different things I was interested in, and one of them was music, and I did composition, I played the piano, a whole variety of stuff…and I pursued that, but I always had an interest in math and science, and I sort of kept that going in the background while I was doing my music major. I was taking some math courses and astronomy courses senior year, and I took a class called Planetary Geology. It was a graduate course, so I was somewhat out of my league, having not done any geology up to that point. I managed to make it through the course, and I got kind of excited, I wrote a term paper that my professor enjoyed about the moons of Jupiter and the possibility of life there. So I graduated as a music major, but the geology sort of stuck with me, and after a couple years I decided to look for a career in it and got into a program at Washington University in St. Louis, and that has one of top programs in planetary geology, and the adviser was tied in with JPL, and that's how I eventually got into JPL.”1

  Once on the track to JPL, there was no turning back. He had been bitten by the Mars bug.

  “I came on as the deputy project scientist, and the guy who I succeeded, Steve Saunders, was something of a mentor for me here at JPL, and I guess he liked having me as his right-hand man, so he brought me onto this project; then he retired and I got moved up to the project scientist position. For the last twelve or thirteen years, I've been focusing mainly on Mars, and I've also worked on two other Mars orbiter projects, [the Mars Reconnaissance Orbiter] and Mars Express.”

  But Mars Odyssey was not initially planned as simply an orbiter. It was something far more complex, in the vein of the Vi
king missions of 1976: “This project actually consisted of both an orbiter and a lander that we were going to fly to Mars. The orbiter was going to land first, and the lander, along with a small rover similar to the Pathfinder rover, was going to land. So the orbiter would have two jobs, one would be to relay the data, as we do now for the Mars Exploration Rovers, and the orbiter would also make measurements around the planet as well as handle the lander's data.

  “That mission unfortunately never flew. We were well in development for the lander part of the Mars 2001 mission, and when we had the twin failures on the Mars 1998 project, which were of course the Mars Polar Lander and the Mars Climate Orbiter.

  “So, half a step in, they said that the Mars 2001 Lander was extremely similar to the Mars Polar Lander, which failed, so they said, ‘Let's still hold on to that, we still have the orbiter.’ [T]hey understood the problems, and it really wasn't any fundamental problem with the orbiter itself, so, we went on and did the 2001 mission and the lander was put on the shelf…and eventually got resurrected as the Phoenix Lander. [It had the] exact same hardware, [was the] exact same unit that was supposed to go to 2001, which eventually went to a 2007 mission and was very successful.”

  In fact, the Phoenix Lander became the first successful landing above equatorial Mars, and the mission, though brief in comparison to Mars Odyssey, was wildly successful. But that's another story.

  One instrument would set Mars Odyssey apart from all previous orbiters, and its name was THEMIS: “It's a unique instrument [that] makes images using infrared vision. Its detector is taken straight out of night-goggle technology, and it sees a part of the spectrum where there are diagnostic spectral signatures of certain minerals that appear on Mars that are not easily detected with other [spectra] on instruments. And another thing unique about it is that it will create global maps of Mars, almost 100 percent coverage of Mars, so basically it makes an image of the planet's temperature. You can see how the surface gets cooled down during the night. [The] rockier areas stay warmer during the night while dusty areas cool down faster, so the camera can really tell us a lot about the terrain on Mars and its texture. The resolution is really incredible, about 100 meters per pixel.”

  Odyssey was well equipped to make history. “I think we're already at the point where we can look back and see what's historical and what really this mission has achieved. There are two different areas. First is the discovery and mapping of ice in the soil. The onboard instruments made unequivocal observations and maps of hydrogen in the subsurface of Mars down within the first couple of feet, and we saw both polar regions and down to about sixty degrees north and south latitudes. [This is] what you might call the Arctic of Mars…just shot through with ice in the soil. There really was no way for anybody to make that measurement before, and make the maps, until Odyssey came along. This provided the target for the Phoenix lander, which set down within this arctic circle. Besides the scraping with its robotic arm and those investigations, the soil was blown away by the descent boosters of the lander, and it uncovered ice right underneath it. So historically speaking, that might be the biggest mark that Odyssey has made and will be remembered for.

  “The whole theme of this Mars exploration program is to follow the water and to understand the possibility of life on Mars. Clearly all life that we know of needs water in its cells and its environment to survive. So it's always been the major goal of the mission to understand the role of water in both the history of Mars and also the evolution of Mars today. It's as if to say, ‘where can we find water [and] the ice,’ and to be able to localize a map, and ultimately have it confirmed for the [landing site]. That was a huge step, to follow the water and touch it with the Phoenix lander. We have several other plans to send landing craft to Mars. None of [the others] are going to these icy terrains, but I think, ultimately, we will go back to some of these icy areas, maybe to find a place where there might be a hospitable environment for some kind of little microbe.”

  But the Mars Odyssey mission was not all guts and glory: “I think the most difficult period during the mission was about two years after we arrived, which was around October 2003. There was a series of huge solar flares, and that resulted in a kind of radiation or magnetic storm at Mars, and it just clobbered our spacecraft. It actually killed off the MARIE instrument; the sensor just measured this radiation and choked on it. The storm also set Odyssey into a safe mode, which is a good thing if a spacecraft's in trouble. It goes into a safe state, where it's not actually required to do a whole lot, but we did lose contact for a time. When we got it back, we saw that it had been rattled, and we had to improvise, press the reboot button and do a complete hard reset of the computer. That is a bit stressful. But other than that we have been very fortunate.”

  So what lies ahead for Mars Odyssey, currently the longest serving spacecraft at Mars? “We are going to go for as long as we can! We are already way beyond our prime mission. One thing that helps is that we served this relay function, we're continuing to do that for the [Mars] Opportunity Rover, [and] hopefully in a year or so, when the Mars Science Laboratory arrives at Mars. We still have good science with the instruments we have around, [and] as long as we have fuel, we still should be able to continue to operate. We just might have another ten years, if we don't run out of fuel or funding.”

  These two factors, fuel and funding, are the great nemeses of robotic exploration of the cosmos. Fuel is a fixed quantity once the craft leaves Earth, but continued funding is something that dedicated explorers like Jeffrey Plaut worry about every day.

  In the first years of the new millennium, spurred by the success of Mars Odyssey, JPL seemed to regain its institutional confidence. Things were working again, and Mars seemed within reach in a way not seen since Viking.

  The next step after the spectacular success of Mars Odyssey, which continued to operate and send back information vital to future mission planning, was a set of dual rovers. These would be an evolution of the Mars Pathfinder mission: similar in design but an exponential leap in scope and ambition. They were the Mars Exploration Rovers (MER).

  These twin rovers, which built on knowledge gained from the successes (and limitations) of the Mars Pathfinder rover, Sojourner, were built at JPL. In general terms, the orbiters tended to be built by outside contractors (Lockheed Martin preeminent among them) while the rovers were built at the lab by internal staff. The design and fabrication of Pathfinder had been exemplary; the Mars Exploration Rovers would outshine even that.

  Each completed spacecraft would weigh in at about 2,400 pounds, with the rovers themselves tipping the scales at about 408 pounds. Rather than depending on the landing stage as a relay for the radio transmissions back to Earth (as Sojourner did), MER would utilize spacecraft already in orbit around Mars, the Mars Global Surveyor and Mars Odyssey probes. It was an ingenious and carefully planned perfection of the capabilities of JPL assets on and in orbit around Mars. The rovers were also capable of communicating directly with Earth, but the orbiters offered a superior conduit for communication.

  The rovers were both far larger and more robust than Sojourner, but with a similar overall design. These too used solar panels for power, and each would arrive on Mars sitting inside a lander shielded by metal petals. The lander itself would follow a flight profile similar to Pathfinder's, and would employ an almost identical landing scheme, right down to the beach-ball cocoon and the multiple-bounce arrival. Why mess with success?

  But while Sojourner had provided a few short weeks of successful operations within sight of its lander, MER would range far and wide over long and active missions. To provide a maximum return on investment, the instrumentation had been beefed up as well.

  For starters, the rovers were loaded with cameras. There was a panoramic camera, mounted on a mast about five feet high, to image the surrounding terrain. On the same mast was a navigation camera, with a wider field of view. This one operated in black and white and for driving and navigation purposes. Below this was a mirror f
or the Thermal Emission Spectrometer, which helps to identify promising rocks and soils for closer investigation. Finally, there were four more black-and-white cameras, two up front and two at the rear, for hazard avoidance. Their sole purpose was to assist in keeping the rovers out of trouble.

  One more imager made up the visual complement: the Microscopic Imager, which would take extreme high-resolution close-ups of the rocks and soils being investigated by the arm.

  The instruments for scientific investigation took their cue from Sojourner and expanded on this theme. These were mounted on the same robotic arm as the Microscopic Imager, which gave the rover even more reach. There was an Alpha Proton X-Ray Spectrometer (an improved version of the APXS on Pathfinder) that could identify the elements of the rocks that the rover would stop and “sniff.” Another device was the Mössbauer spectrometer, used to investigate iron-bearing rocks and soils.

  Less high-tech but still useful was the oddly named “RAT,” or Rock Abrasion Tool, which would dust off or, if necessary, grind down the surface of rocks to be examined. This allowed for a clean, fresh surface to test with the various devices. And last but not least, there was a collection of magnets, to pick up any ferrous material from the RAT or from the environment at large, which the Mössbauer spectrometer would more closely analyze. This device is particularly adept at identifying iron-bearing minerals that other devices may not be able to “see” when present in small amounts. It can sense the magnetic properties of samples and potentially identify materials formed in hot and wet environments. If there was a downside of this particularly valuable device, it was that a thorough reading took up to twelve hours. But the rovers would have plenty of time.